The Eustachian tube (‘ET’), also often referred to as the ‘auditory tube’ connects the middle ear cavity to the back of the nose/throat (nasopharynx). The ET is a tube a third of which is made of bone, the rest cartilage. In a human, the ET is normally closed with its wall collapsed, but it can open to let some air through in order to equalise the pressure between the middle ear and the outside environment. Opening in this way may be accomplished by swallowing, yawning, or chewing. The inability to voluntarily regulate or attain pressure equalisation (for instance, during aircraft flights, underwater diving, or due to certain disease states) creates a blockage which is often referred to as ET dysfunction.
The ET also serves to drain mucus or fluid from the middle ear. The ability of the ET to act as an efficient drain diminishes when blocked by pressure imbalances. Blockages of this nature may occur from upper airway infections or from allergic responses. The most common symptom of ET blockage is earache which is often more prevalent in children because the ET is shorter and more horizontal, the latter makes drainage of fluid harder. Also, depending on the severity of the blockage there may also be various levels of hearing impairment associated with ET blockage. There are also children born with an inherent weakness of Eustachian tube function. This may be a genetic phenomenon.
There are a number of diseases in which Eustachian tube dysfunction represents the primary underlying pathological mechanism and hence represent potential therapeutic indications. The most common group of therapeutic indications is Otitis Media (OM) otherwise known as inflammation of the middle ear.
OM has various attributes and while terminology and definitions are not universally agreed, it is possible to describe the following:
Acute Otitis Media (AOM) is characterised by rapid onset and short duration of signs and symptoms which may be local (such as otalgia) and/or systemic (fever and vomiting). During the early phases of infection, AOM may not be associated with effusion (fluid in the middle ear). However, effusion is a consequence of AOM. Relief of symptoms generally occurs before clearance of effusion.
Otitis Media with Effusion (OME) (also known as Serous Otititus Media, Secretory Otitus Media or by the lay term as “glue ear”) occurs when a blockage in the eustachian tube leads to negative pressure in the middle ear and a transudate of fluid drawn from middle ear mucosa. The effusion may be serous, mucoid or purulent (or a combination of these). OME may follow AOM or occur without prior AOM. OME is often longer lasting (subacute or chronic) and often asymptomatic.
OME is usually treated by inserting small tubes (called ventilation tubes) into the tympanic membrane (or ear drum), which facilitates drainage of any accumulated fluid in the middle ear, and also continually equalizes the pressure in the middle ear. Unfortunately however, the insertion of ventilation tubes in this manner requires invasive surgical intervention. In addition, keeping the ET open with ventilation tubes also increases the risk of infection from the environment and via the ET, due to the loss of an air cushion.
Aerotitis Media (AM), (also known as barotrauma or “ear block”) occurs following an increase in ambient air pressure such as when flying or during the use of a hypobaric chamber. The resulting pressure differential between the middle ear and atmosphere stretches the tympanic membrane producing discomfort or pain. Other symptoms may include slight hearing loss, sensation of fullness in ears and dizziness.
OM is a major world wide health problem. It is the most common illness for which children receive medical care in the United States and in most of the developed and developing countries in the world. Statistics indicate that 24.5 million physician's office visits were made for OM in the United States alone in 1990, representing a >200% increase over those reported in the 1980s. It is estimated that 83% of all children will experience at least one episode of acute OM (AOM) by 3 years of age and that more than 40% of children will experience three or more episodes of AOM by this age. Although only very rarely associated with mortality any longer, the morbidity associated with OM is significant. Otitis media with effusion (OME) is the commonest cause for acquired hearing loss in childhood with behavioural, educational, and language development delays being additional consequences of its early-onset.
Apart from the surgical solutions referred to above depending upon the cause and severity of the symptoms associated with ET dysfunction, physicians may prescribe decongestants, antihistamines or steroids. Decongestants and antihistamines are believed to reduce swelling of the mucosa, but there is no scientific proof that decongestants or antihistamines facilitate Eustachian tube function. Steroids have the disadvantage that they are potentially associated with severe side effects.
The present invention is directed to providing an effective treatment for ET dysfunctions which beneficially relieves some or all of the symptoms associated ET disorders or dysfunctions.